Stereomicroscopes of this kind are used, in particular, in opthalmologic and neurosurgical operations. In such cases a binocular tube, through which the surgeon or principal surgeon can observe the object stereoscopically, is arranged after the beam splitter device. Stereomicroscopes of this kind can be of the telescopic type (Galilean system), one main objective common to both main beam paths being arranged on the microscope body. Also known are microscopes of the Greenough type, in which one objective is provided for each main beam path. A magnification changer or zoom system is often placed after the objective. This allows a variety of fixed magnifications, or a continuous magnification range, to be achieved. One channel of a magnification changer (zoom system) is provided for each of the two channels (main beam paths) of the stereomicroscope, such that both magnification changer/zoom system channels are to be adjusted or displaced synchronously. With such a configuration, the aforesaid beam splitter device is usefully arranged after the magnification changer/zoom system. Stereomicroscopes of this kind are sufficiently known and therefore will not be discussed in detail here.
When a stereomicroscope of this kind is used as a surgical microscope, an assistant's beam path is often coupled (faded) out of one of the two, or both, main beam paths, and directed to an interface for an assistant's tube, allowing the assistant or co-observer to view an image of the object through said assistant's tube. When the assistant's beam path is coupled out of only one of the two main beam paths, a monoscopic (non-three-dimensional) image is present. An assistant's beam path of this kind can, however, be split into two channels (small stereo base) in the assistant's tube, so that a stereoscopic image with less of a three-dimensional impression can be obtained. It is also useful and known to couple out a documentation beam path that is delivered to a documentation module or to a documentation device. These documentation modules can be, for example, electro-optical imagers (CCD arrays) or other image memories, which can acquire and store image sequences or individual images. By means of such documentation devices, for example, the course of an operation can be recorded for documentation purposes, or individual images of the object can be stored for later analysis.
Be it noted in this connection that the terms “assistant's beam path” and “documentation beam path” were selected merely for better illustration of the use of the stereomicroscope according to the present invention, and can be replaced by the general terms “secondary beam path” and “tertiary beam path,” respectively, if these beam paths are to be used differently. The discussion below will refer, for reasons of simplicity, to assistant's beam paths and documentation beam paths, without limiting the invention to a stereomicroscope having corresponding assistant's or documentation modules.
In the context of the aforesaid surgical microscopes, a desire exists to place the assistant or co-observer selectably on the left or the right side of the microscope. It is known for this purpose to couple out an assistant's beam path from both the left and the right main beam path, and direct it to a corresponding interface on the microscope housing. If the corresponding microscope is equipped with only one assistant's tube, however, the latter must be reinstalled from one side to the other upon an assistant changeover. Such installation entails risks and sterility problems. For reasons of weight and cost, the provision of two fixed assistant's tubes would not be advantageous.
Solutions additionally exist in which the assistant's tube is embodied pivotably in a horizontal plane. The horizontal plane here represents a plane that extends perpendicular to the plane containing the two main beam paths of the stereomicroscope. These solutions require two additional assistant's main beam paths proceeding parallel to the two main stereo beam paths, resulting in a complex four-beam microscope construction. A further disadvantage of such solutions is that the main observer's tube must first be removed, or at least swung aside, before the assistant's tube can be pivoted.
EP 1 486 813 A1 discloses a surgical stereomicroscope having an assistant's tube that is arranged on the rear side of the microscope, pivotably in a plane parallel to the main stereo beam paths. The main observer's tube is arranged on the front side of the microscope. The assistant's tube is guided out toward the rear on the rear side of the microscope, and can be pivoted from the left to the right side and back, depending on the assistant's desired position. Outcoupling of a documentation beam path is not addressed here. With an arrangement of this kind, application of a counterweight to the pivotable assistant's tube is advantageous for reasons of stability. This once again turns out to be disadvantageous in practice, however, for reasons of cost, weight, and alignment.
DE 195 04 427 B4 discloses a stereo microscope having a single optical system, i.e. only one channel, the main objective and a magnification changer being followed by a beam splitter element. The beam splitter element couples a secondary observation beam path out of the primary observation beam path. The beam splitter element involves of three separate prisms. Located after the beam splitter element are two optical elements, arranged adjacently to one another, that supply an intermediate image of the object being viewed, said image being detected by two electro-optical image sensors. A configuration of this kind is suitable for a video stereomicroscope. The secondary observation beam path is also imaged onto an image sensor of this kind. The entire optical system of the secondary observation beam path, including the beam splitter element, is mounted rotatably about a rotation axis that extends through the pupil used jointly by the primary and the secondary observation beam path. This proposed design is not suitable for a double-beam stereomicroscope. Here the beam splitter rotates about a correspondingly wide channel of the main beam path. This document also does not address the outcoupling of a further tertiary (or documentation) beam path.
Lastly, U.S. Pat. No. 5,552,929 discloses a stereomicroscope having a main observer's tube, a co-observer's tube, and a documentation output. This, too, involves a so-called “Single Optical System” in which the split into two beam paths is performed only in the tube. Outcoupling of the beam paths into a beam path for the main observer and co-observer is accomplished using beam splitters that are arranged in a correspondingly wide channel of the main beam path. The design proposed here is not suitable for double-beam stereomicroscopes, since in the latter, the image would also rotate upon pivoting of a tube. Prisms would therefore in turn need to be provided in order to rotate the image back.
In other known double-beam stereomicroscopes, a so-called (semi-)stereo assistant has hitherto been attached laterally on the beam splitter. The latter is not pivotable, since the (video) documentation system, to which the second main beam path is delivered, is already attached on the opposite side. The absence of a capability for assistant changeover is very highly disadvantageous here for the user. Other solutions, already addressed, utilize a four-beam microscope configuration that results in stereomicroscopes in a substantially higher price class.